1. Field of the Invention
The present invention relates to a molding machine which is used for die-casting, injection molding, and blow molding and the like, and a molding method using the same molding machine.
2. Description of the Related Art
Conventionally, a molding machine, for example for die-casting, has a structure as shown in FIG. 15, wherein four tie bars 4 bridge between a fixed platen 2 and a supporting mount 3 secured at each end portion of a base plate 1. The tie bars 4 are inserted into a movable platen 5 which is slidably mounted on the base plate 1, and the movable platen 5 is advanced along the tie bars 4 to the fixed platen 2 side by die opening/closing and die clamping means 6 which is disposed between the supporting mount 3 and the movable platen 5. Accordingly, a movable die 8 supported by the movable platen 5 in relation to a fixed die 7 supported by the fixed platen 2 is closed, and at the same time, a clamping force is generated between both. Note that reference numeral 9 denotes an injector 9 provided on a back side of the fixed platen 2 for injecting molten metal to the mold. In general, an injector like this employs the die opening/closing and die clamping means 6 equipped with a toggle mechanism 6b which is driven by a cylinder 6a as a driving source, as shown in this drawing, since such die opening/closing and die clamping means 6 is capable of applying a large clamping force to the mold.
Meanwhile, small-scale production of a wide variety of products is common in recent production lines, and a mold changing cycle has been significantly shortened. Furthermore, a component to be molded by casting, injection molding or the like are becoming more and more complicated or large-sized, which inevitably reduces the lifetime of a mold and increases frequency of mold changing. Particularly, in die-casting where a high temperature molten metal is filled into a mold at a high speed and high pressure, the mold is so damaged that it needs to be changed quite frequently. However, in a common molding machine as shown in FIG. 15, there are four tie bars 4 around the fixed die 7 and the movable die 8, and these tie bars 4 not only hinder mold changeover work but also make installation of an automatic die changeover machine difficult.
Meanwhile, a molding machine for die-casting requires various types of peripheral devices (incidental equipment) including a molded component extraction device, a die lubricant application device, a cast product (insert) attachment device and the like. However, since the tie bars 4 described above restrict an installation space and a working range of the incidental equipment, designing under constraints (after-design) is compelled. Therefore, durability and reliability of the incidental equipment is impaired, which is a major cause for reduced rate of operation of the molding machine.
Meanwhile, in the field of injection molding, as disclosed in Japanese Patent Application Laid-Open Nos. 9-201855 and 7-148807, an injection molding machine is proposed. In this injection molding machine, one end portions of four tie bars are respectively supported by a movable plate (movable platen), and a lock mechanism provided on a fixed plate (fixed platen) locks and unlocks the other end portions of the tie bars. Furthermore, die opening/closing means advances the movable plate toward the fixed plate so as to close a fixed die on the fixed plate and a movable die on the movable plate. Next, the lock mechanism secures the other end portions of the tie bars to the fixed plate. In this state, die clamping means built into the movable plate (as disclosed in Japanese Patent Application Laid-Open No. 9-20185) or die clamping means provided in a tie bar insertion portion of the fixed plate (disclosed in Japanese Patent Application Laid-Open No. 7-148807) is actuated to generate a clamping force. After molding, at the same time when the lock mechanism is actuated to execute unlocking operation allowing the die opening/closing means to open the mold, the four tie bars are removed from the movable plate.
However, according to the injection molding machine as disclosed in the two patent documents mentioned above, although the four tie bars are removed from the fixed platen at the same time of the die opening, the tie bars are not completely evacuated from the periphery of the mold. This results in not only insufficient improvement in changeover operability but also insufficient improvement of space limitation with regard to the incidental equipment. Note that in the injection molding machines as disclosed in the two patent documents, a countermeasure is taken where a cylinder for removing the tie bars is provided on a top portion of the movable platen (movable plate, or movable die plate), which causes only the upper tie bars to retreat after the die opening. However, since the lower tie bars remain in the periphery of the mold still with the die in an open state, improvement of the space limitation with regard to the incidental equipment is still insufficient, and thus the countermeasure does not solve the problem fundamentally.